Telegraph system



Filed June 3,1942 2 Sheets-Sheet 1 7'0 Ti F/GJ.

R7 3 Irr/ 79R HTS 1 M RRS July 25,1944. F. P. MASON r 2,354,534

TELEGRAPH SYSTEM Wm y July 25, 1944. F. P. MASO N TELEGRAPH SYSTEM Filed June.3, 1942 2 Sheets-Sheet 2 F/ G. a;

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Patented July 25, 1944 UNITED STAT ES PAT OFFICE 2,354,534 I I p TELEGRAPH SYSTEM. v Frederick Percival Mason, Croydon, England; Sign Creed and pany Limited; oro aon, I England, a. British company I Application June 3, 1942,. Serial .No..445,567 In Great Britain Novembcr29; 1940' 5 Claims.

This invention is an improvement in or mod.- ification of the invention disclosed in Patent No. 2,242,196 issued to Thompson on May 13,1941. It relates to printing telegraph systems for operation in circumstances in whichinterference tem is repeated if the signal has not been correctlyreceived and printing in accordance with the incorrectly received signalv combination is prevented by the transmission of acharacteristic signal combination,

Alsov according to the invention, a printing telegraph transmitter system comprises means for transmitting a signal combination, means for automatically comparing a received signal combination with the transmitted signal combination, and means for thereupon transmitting a characteristic signal combination whenever the transmitted and received signal combinations are difierent.

Also according to the invention, a printing telegraph receiver system comprisesmeans for, receiving a, signal combination, means 'forretransmitting the signal combination as received; and ,means for printing a character corresponding to the received signal combination unless prevented by the receipt of a-characteristic signal combination.

An embodiment of the invention Will now be described by way of example, reference-being. made to the accompanying drawings, in which Figs. 1 and 1a are connecting halves of a diagram of my system, showing circuit details of apparatus at the traffic ofiice T0;

In Figs. 1. and la, RTS represents a radio transmitting station, RES represents a radio receiving station, and TO represents a traflic omce provided with an impulse transmitter for transmitting telegraph impulses to RTS and ,a multiplex printer for receiving telegraph impulses from RRS. Similar apparatus is. provided at a distant terminal to complete atwo-Way radio telegraph link.

The traffic ofiice TO also includes a checkback circuit and asensitivity controlcircuit, the functions of which will be explained later Signaling over the radio linkv is effected by the radio transmitter RT at the radio transmitting station *RTS and the radio receiver RRR at the radio receiving station RRS; Any desired methodimay beeinployed for the radio trans, missionof the marking and, spacing telegraph signals but it will. be assumed. that; they are transmitted as, interruptionsv of a, continuous, unmcdulatedcarrier wave, theemission of carcier representing, a spacing. signal and the I absence of carrienrepr'esenting amarking signal. The radio receiver BBB is, provided withv two output. circuits... One output circuit lof'RRR is connected to a low-passfilter S .toprovide a .signalpath-connectedt a valve conversion. circuit- VCC the output, of which isj.applied to a valve. relaycircuit VRC which repeats the markingand-spacing telegraph impulses. The other 7 output-circuit of .RRR is connected to a band'- pass filterN theoutput from which is applied over an interference path-tea second input. to' the. conversion circuit VCC.. Circuit details of VCLC..and.VRC are-we'lhknown' in. the art and. these elements. may. Conveniently take the vform shownlin British Patent No. 540,839. Itwi ll be. sufiicient to state atthis point that VRC acts, as an. impulse repeating arrangementofhigh efi'iciency and that vVCC acts underthe joint con.-

trol .of. the signal path and the interference path to cause the impulse respondingapparatusVRC to take up the, same predetermined condition when the radio transmission is; disturbed, whether by interference or by fading; 1 The circuits are modified, according tothe'invention by the inclusionof arelay RBprovided'with con-.

- tact rbl connected in serieswithj a battery B,

' and. L2.

the. series combination being shuntedflacross a resistance R! in thesignalpath. fI'heQreIay RB is controlled from traflic officeTO over leads Ll The arrangement .used comprises five distributor. rings shown diagrammatically at TR, TL, RS, RRand RB, each shown as La brushrotating over a ringof" segments. Each of these'distributorrings is of the. well known type in which'a rotating. brushconhectsa segmented ri With a. continuous ring, the.- continuous. rings. being connected to thefcircuits to which therespective brushes are shown in .thedrawingsas connected.- Thedistributor rings .TR and. TL are allocated to transmission. and the. distributor rings RS,: RR andRL to reception. The brushes of allthe ringsaare driventogethenand any well known meansimay. be v usedvfor keeping. the brushes (at the. two trafiic; offices inasynchronism. One; method. will be. describedhereinafter. .It will bereadilyunderstood. by, those skilled, in the art, however. that the brushes Wiping over 'rings'RS,

; RR and RL are adjusted to be later inphase.

to the Well known five unit code, are determined by a transmitter controlled by a perforated tape. This transmitter is of the well-known kind in which peckers controlled by perforations in the tape determine the connection of contact points TTI-TT to marking or spacing bus bars 32 or 3I respectively, which bus bars are connected to negative and positive battery respectively. The

contact points TTI-,-TT5 are connected to se ments I-5 of distributor ring TR and as the brush rotates overthese segments positive and negative potential is connected by the brush to a transmittingrelay TRR. Contacts trrI of relay TRR connect negative (marking) or positiv (spacing) potential over the line L5 to modulate the radio transmitter RT'in well-known manner and cause the transmission of radio signals to the distant terminal.

At the distant terminal the radio signals are received by a radio receiver similar to BBB, demodulated, and the'resultant telegraph signals applied over lines similar to L3 and L4 to a polarised receiving, relay similar to RRA at ofiice Y. Contacts rra'l connect negative or positive potential, according to the polarities of the received telegraph signals, over segments I5 of distributor ringRR to relays CACE and to negative battery. Those relays to which marking potential is applied from contacts rml do not energise, those relays to which spacing potential is applied, energise and close contacts caIi-cel, and ca2-ce2. r Contacts cal-eel close a lockin circuit for the relays thathav'e been operated. Contacts cc2-ce2 connect relays EAEE to segments I2-I 6 or distributor ring RL.

If any of the contacts caI-cel are unoperated, negative (marking) potential is connected over the corresponding relay CA-'CE to the corresponding segment of the segments 6-H) of the transmitter TR at ofiice Y, whilst if the contacts cat-eel are operated, positive (spacing) potential is connected over contacts gal in normal position andthe operated contacts caIceI to the segments 6-40 of ring Ofiice Y will thus transmit back to office X the signals asreceived.

At office X the receiving brushes are passing over segments6'I II as the signals re-transmitted from Y' are received at X. The segments 6-40 of ring RR are connected to the contacts TTI TT5 of, the perforated tape transmitter. If the signal sent by contact TT I was a'marking signal, a marking signal should be received from contacts rral over segment 6 of ring RR. Two relays BA and BB are provided, BA being connected between negative battery and bu bar 32, and relay BB between positive battery and bus bar 3|. Thus if a marking signal be received and contacts rral are in marking position When the brush passes over segment 6 of ring RR, both sides of relay BA are at marking potential and the ciredit of BB is open so that no current flows. If a spacing signal had originally been transmitted by th tape controlled transmitter so that contacts TTI are "connected 'to spacing bus bar 3|, and a contacts fI spacing signal is received then contacts rraI will apply spacing potential over segment 6 of ring RR to contacts T1I andbus bar 3|. Both sides of relay BB are spacing potential and the circuit of relay BA is open, so that no current flows.

It will be seen therefore that if the received signal combination is the same as the transmitted signal combination neither relay BA nor BB energises. Should, however, any one of the elements of the combination received be different from the corresponding element as transmitted, either relay BA or BB is energised and either contact bal or contact bbI is opened.

Relay F is energised when the brush passes over segment I of ring RL and closes a locking circuit for-itself over contacts baI, bbI and front In this condition of relay F, segments I4 to 22 of distributor ring TR are all connected to marking potential, since all of these segments are directly connected to negative battery except I5, ll, 20 and 22, the latter being connected to switch f3 of relay F which in said condition is set for connection through resistance IR to negative battery. Consequently if relay BA or relay BB is not energised, a signal consisting of nine marking elements is transmitted, and as a result the transmitted character is printed at the receiver. Relay H is energized over segments I3 to I6 of distributor ring TL, and at contacts hI a circuit is completed from positive battery, resistance 5R, contacts hI, front contacts f2, stepping magnet TT of the perforated tape transmitter, negative battery. The tape of the transmitter is thereby stepped forward and controls contacts TTI-TT5 for the next combination.

If on the other hand, either relay BA or BB is energised, the locking circuit of relay F is broken at contacts baI or bbl, and at contacts f3 spacing potential is connected to segments I5, I1, 20 and 22 of ring TR so that a non-printing signal is transmitted. The circuit of the stepping magnet TT cannot be completed, being open at contacts f2 and consequently, during the next rotation of the brush over the distributor ring TR the same character combination is again transmitted over segments I-5.

At' ofiice Y the non-printing signal, if transmitted, is received whilst the brush of the receiving ring-RR is passing over segments I4 to 22. If a non-printing signal is not received, contacts rml ar at this time in marking position and negative potential is connected over these segments toone side of relays DA, DB and DC, the other side of which is also connected to negative potential. Consequently none of these relays energises. I

As the brush of distributor ring RL passes over segments I2 to I6, relays EAEE are connected in operating circuits over'contacts ca2ce2 of the relays CACE that had previously operated. Thus the combination of the relays CACE that had been operated is transferred to the relays EAEEand those of the latter relays that operate close locking circuits for themselves over contacts eaIeeI and contacts gbI to earth. The relays CA-'-CE that were previously operated and had closed locking circuits for themselves are unlocked when the brush of ring RL passes over segments 20 and 2I. When this happens relay GA is energised and at contacts gal opens the locking circuits for relays CACE. Contacts ea2ee2 prepare circuits for the magnets PMI- PMS of the multiplex printer. As none of relays DA, DB and DC has operated, the circuit for those magnets is completed; over-segment 2 of;

ring RL, and the signal combination-duly operates the printer. The multiplexprinter may be a but modified so that contact BB-is closed by the operation of any ofthe bars controlled bythe magnets PMI PM5. If anyof these bars is operated, contactiill isclosed and the printer magnet PMR isoperated to effect the printing-of thereceived character. V

If, however, a non-printing signal is transmitted from office X the signal sequence S, M, S, M, M, S,- M, S (where M is a marking signaland S is a spacing signal) is-radiated from the radio transmitter RT and in the absence of atmospheric disturbances the same combination will be received at the radio receiver BER, and repeated to the trafiic office at Y so that the corresponding marking and spacing impulses are applied in turn to segments E5 to 22 of the distributor ring RR.

The first impulse of the combination S, M, S,

M, M, S, M, S is a spacing impulse and is applied over segmentjifi of ring RR to relay DA which thereupon operates and closes a locking circuit for itself over contacts dai. The second impulse is a marking impulse and is applied over segment [6 but 'does not operate relay DB as it is of the same polarity as the potential connected to the other side of relay DE. The third impulse is a spacing impulse and is applied over segment I! to relay DC which thereupon operates and closes a locking circuit for itself over contacts dcl. Contacts daZ and (02 open the. printer magnet circuit and no printing can take place. Thefourth and fifth impulses are marking impulses which are without effect. The sixth (M), seventh (S) and eighth (M) impulses are a repetition of the first, second and third impulses and like them constitute the characteristic combination forming the non-printing signal. Thenon printing signal is thus. sent twice so as togive relays DA and DCtwo chances of responding.

Relays DA-DC and EA-EE are unlocked by en-.-

ergizing relay GB through engagement of the brush of ring RL with the segments 5, and 6, thereby opening switch gbl in the locking circuits.

It-will be appreciated that the circuit is so arranged that printing will always take place unlessv a non-printing signal is received. This nonprinting signal consists of a characteristic signal combination (S, M, S) which is unlikely to be accidentally received as a consequence of radio disturbances. It is extremely unlikely, for example, that if interfering carrier is present it will be so disposed as to cause the operation of relays DA and DC whilst leaving relay DB unoperated. It is essential. that relay DB remains unoperated for the non-print to be carried out since if it operates it immediately recloses the print-. ing circuit which relays DA and DC have opened.

In order to guard against loss or distortion of the non-printing signal due to fading, the characteristic signal combination is sent twice. The number of extra characters printed is thereby greatly reduced whilst at the same time the chances of two stray radio impulses occurring at very small. Also, the two non-printing signals are-separatedby two marking signals so as to.

disturb what would otherwisebe aregularalten nation of 'marking, and, spacingisignals and thus; make it unlikely for reversals transmitted on an adjacent carrier wave-to producethe effect of. non-printing signal.

synchronisation of the distributors is shown as being achieved by means of'the well: known system described with reference to Fig; 313 on p. 3120f the book by H. H. Harrison entitled: Printing'Telegraph Systems and Mechanisms, the correcting magnet CM being shown connected to segment l2 of distributor ring RR; From segments II and I2. of the distributor ringTR two impulses of opposite character are sent..- If the impulse sent out over segment H arrives. at the other station over segment ii, the correcting magnet CM is operated to set back the phase of the receiving distributor. It will be: noted that this impulse is of the opposite character to that of the printing impulses and this ensures that disturbances will not insert a'false; correcting impulse.

Switches SI, S2 and S3 are provided in order: to permit of definite conditions being applied. to all the segments of the distributors to ensure: rapid initial synchronisation. Switch Si when operated short circuits relay GA and soprevents locking of the relays CA-CE and ensures that marking=,potential is applied to segments :6 to It of ring TR. Switch S2 short circuits the bus bars 3! and 32 and maintains segments I to 5 at marking potential. Switch S3 ensures: that relay F remains operated and this applies marking potential to segments i l to 22.

Whenever the check back circuit (C BC in" Fig. 1) at X determines that the transmitted character has been correctly received at Yrelay F at X remains operated and a succession of nine marking impulses is'transmitted whilst the brush passes oversegments I i-22 of ring TR. These impulses, which are transmitted as'a long. period of no-carrier, produce no effect on relays DA, DB, DC at Y and printing takes place.

Inthesystem described in Patent 2,242,196 the non-printing signal is transmitted'by cause, ing relay F on releasing to connect all the seg ments !5 22;of ring TR to spacing potential, so that a long spacing signal is transmitted to effect the operation of a relay D which opens the operating circuit of the printer. In these circumstances the non-printing signal is transmitted as a long period of carrier energy.

Moreover, in order to deal more effectively with radio disturbances, the effects ofatmos= pherics and similar interference were converted into that of fading so that the only disturbance requiring further consideration was that of fading. This feature is retained in the present modified systems, 7

During disturbed atmospheric conditions, therefore, fading effects will be present in the receiving circuits with the result that character signals will be incorrectly received and manynon-printing signals will be transmitted (as long periods of carrier energy). Many of these nonprinting signals, however, will be wholly or partially faded out; the resultant tendency being to, convert them into printing signals and so to cause the printing of a large number of unwanted extra characters. number of such extra characters the circuit of Patent No. 2,214,196 was so arranged that any carrier arriving during the printing signal period would act as a non-printing signal by effectingthe operation of relay D. This, however,

,had :thedrawback that any straycarrier energy In order to reduce the.

on, or sufliciently close to, the working carrier frequency'would cause a printing signal (absence of carrier) to be converted into a non printing signal (presence of carrier) with the resultant loss of a desired character.

This drawback is overcome, according to the present invention, by arranging to print in all cases where a non-printing signal is not received, the non-printing signal being of such a character as to ofier the minimum chance of its being simulated by stray carrier energy, as already explained.

In order to reduce still further the number of extra characters printed during the existence of disturbances, the sensitivity control circuit is provided. The object of this circuit is to decrease the sensitivity of the receiver during the reception of the code elements as compared with its sensitivity during the reception of the non-printing signal.

For this purpose the apparatus at the trafiic office T is provided with an additional receiving ring RS having its segments I5 connected to earth. The battery is thereby connected to lines LI and L2 respectively to effect the operation of a relay RB at the radio receiving station RRS whilst the brushes at the trafiic oflice T0 are passing over segments I5, i. e. While the code signals are being received by the receiver RRR. Relay RB upon operating connects a battery B across a re-.

sistance R in the signal path. Battery B is connected in such a direction as to reduce the sensitivity of valve V3, and therefore to reduce the amplitude of the code signals fed to the valve relay circuit VRC.

During disturbed atmospheric conditions, a large number of transmitted signal elements will be lost, and, as already explained, this leads to.

Stage Code signals Non-printing signal 1 Correct Absent (not transmitted).

Failing. Correct.

Failing. Absent (faded out).

It will'be seenthat as soon as the non-printing signal begins to fade out, the code signals are completely faded out. This absence of code signals conditions the printer for a non-print, non-feed function so that even though the loss of the non-printing signal may result in the printing function being performed no character will actually be printed.

What is claimed is:

1. A printing telegraph system including sig nal transmitting means at a transmitting station, signal receiving means at a receiving station including printing apparatus, means for retransmitting a received signal combination from the receiving station to the transmitting station. means at the transmitting station for receiving and comparing the re-transmitted signal combination with the original signal combination, and means for controlling the operation of the printing apparatus in accordance with theresults of said comparison, comprising means-at the transmitting station for sending a non-print signal combination when the compared signals differ, said non-print signal combination comprising a transmitted carrier wave element and a signal element consisting of a period of nontransmission in sequence, said control means ineluding a first relay operative by said transmitted signal element so as to open the printing cirsuit and a second relay operative by said signal element comprising a non-tranmission period and also operative by interference waves so as to close the printing circuit, the arrangement being such that interference waves received during the reception period for said carrier wave element and also during said non-transmission period will be ineffective to actuate the preventing means.

2. A printing telegraph system including signal transmitting means at a transmitting station, signal receiving means at a receiving station including printing apparatus, means for retransmitting a received signal combination from the receiving station the transmitting station, means at the transmitting station for receiving and comparing the retransmitted signal combination with the original signal combination, and means for controlling the operating of the printing apparatus in accordance with the results of said comparison comprising means at the transmitting station operative when the compared signals differ to send a non-print signal combination comprising acarrier wave element and an element consisting of a period of non-transmission in sequence, and means at the receiving station selectively responsive to said non-print signal combination for preventing the operation of the printing apparatus, said preventing means comprising an operating circuit for the printing mechanism, including a normally closed switch and a normally open switch in parallel, a relay for opening the closed switch, means for energizing the relay during the period of reception of the carrier wave signal element, a relay arranged to close the normally open switch and means for energizing said relay when an interference wave is received during the period of reception of said non-transmission element, the arrangement being such that said circuit will remain closed when interference waves are received during both of said signal element reception periods.

3. A printing telegraph system as set forth in claim 2, in which the non-print signal sending means includes means for repeating said signal and the selectively responsive means at the receiving station includes means for energizing said first mentioned relay successively upon receipt of said successive signals.

4. A printing telegraph system as set forth in claim 2, in which the non-print signal includes a second carrier wave signal element in sequence with the non-transmission element, a third re' lay, means for energizing the third relay upon receipt of said second carrier wave element, and a second normally closed switch opened by' said third relay and located in said circuit in parallel with said switches.

5. A printing telegraph system comprising signal transmitting means at a transmitting station, signal receiving means at a receiving station including printing apparatus, and means for controlling the operation and non-operation of the printing apparatus by signals from the transmitting station, including means for sending a carrier wave signal element and providing a period of non-transmission forminga second signal element 1n sequence, a printing apparatusoperating circuit at the receiving station, a first relay operative by said transmitted signal element so as to open the printing circuit and a second relay operative by said signal element comprising a non-transmission period and also operative by intereference waves so as to close the printing circuit, thereby maintaining the opera tion of the printing apparatus, even upon receipt of an interference wave of similar frequency during the period of said non-transmitted signal 5 element.

FREDERICK PERCIVAL MASON. 

